This is a simple interface to the LAPACK routines dgeev and zgeev
that sets those routines’ flags to return only the eigenvalues of
general real and complex arrays, respectively.

Examples

Illustration, using the fact that the eigenvalues of a diagonal matrix
are its diagonal elements, that multiplying a matrix on the left
by an orthogonal matrix, Q, and on the right by Q.T (the transpose
of Q), preserves the eigenvalues of the “middle” matrix. In other words,
if Q is orthogonal, then Q*A*Q.T has the same eigenvalues as
A: